Doing everything right?

Hi everyone! I need some help - I am 37 and was diagnosed with hypothyroidism in my latest pregnancy ( I have since been medicated on Synthroid - 100 mcg) . He is 7 months now and I am trying my best to lose weight. I have been staying under the calories and exercising and I lost 6 pounds the first week but gained two back so far with no change to my diet - I know it is early but am I doing something wrong? Feel free to friend me to see my food list - and also how often/long did everyone exercise when they first started out? I find long exercising very difficult at this current weight. Thank you so much! ~ Jess